Children could have a lower risk of developing a peanut allergy if their mothers eat more nuts in pregnancy, researchers claim.

Their study adds to growing evidence that eating nuts while expecting a baby has no damaging effect on the unborn child.

Those with peanut allergies can develop breathing problems if they eat or come into contact with nuts. The most severely affected are at risk of life-threatening anaphylactic shock.

Pregnant woman are now being told eating nuts during pregnancy could reduce a child's risk of developing a nut allergy, contrary to previous advice

Mothers-to-be were previously advised to avoid peanuts, especially if there was a history of allergies such as eczema or asthma in the family, for fear of the baby developing a sensitivity to nuts. One in seven who are sensitive go on to develop allergies.

But now doctors see little harm in peanuts and other nuts, unless the mother herself already has an allergy. In the latest study, researchers looked at data held on 8,205 children.

Dr Ruchi Gupta, of the Northwestern University Feinberg School of Medicine in Chicago, said the study showed that women should not restrict their diets during pregnancy.

‘Certainly, women who are allergic to nuts should continue avoiding nuts,’ she said. ‘Pregnant women should not eliminate nuts from their diet as peanuts are a good source of protein and also provide folic acid, which could potentially prevent both neural tube defects and nut sensitisation.’

The number of British children allergic to peanuts has doubled in the past 20 years for reasons which remain unclear.

Until recently parents were advised to avoid giving children peanuts until the age of three in a bid to reduce allergies. Women are now told they can eat peanuts, or food containing peanuts, during pregnancy unless they are allergic to them or a health professional advises against it.

Indeed some doctors believe exposure to peanuts early in life primes a child’s immune system which defuses the threat of developing an allergy.

Dr Adam Fox, a consultant children’s allergist at Guy’s and St Thomas’s NHS Foundation Trust, said: ‘The results of this study are interesting but contradict other studies that have either shown no effect of nut consumption during pregnancy or suggested a possible risk from increased consumption.

The advice applies to all mothers, except when they have a nut allergy themselves

'To make things even more complicated, there is also strong evidence to suggest that nut allergy doesn’t develop until after birth and that it is exposure of the infant’s skin to nut protein that is most important in the development of allergy.’

He said the latest international guidelines suggested ‘no need to either avoid nuts, nor to actively eat them’.